Robert Lefkowitz of the Howard Hughes Medical Institute at Duke University and his former postdoc, Brian Kobilka of Stanford University, are the recipients of this year’s Nobel Prize in Chemistry. The two researchers work on one of the most important problems in biology: How cells receive and act on information from their environment. Using a range of experimental methods—including radioactive labeling and x-ray crystallography—Kobilka and Lefkowitz have elucidated the structure and function of a class of proteins known as G protein-coupled receptors (GPCRs). GPCRs span cell membranes. When, say, a hormone molecule on the outside of a cell binds to a GPCR, the protein’s structure changes such that the part of it that protrudes into the cell’s interior becomes more attractive to G proteins. The double-binding process then sets off a chain of signaling reactions that are ultimately manifested in a response.